Alcohol use by aircraft pilots is a continuing matter of concern. A substantial number of aircraft accidents have been found to be alcohol related, and many other such accidents may have escaped detection. While the dangers of piloting an aircraft while intoxicated are obvious to most, there is relatively little data available and less agreement concerning the effects of moderate and low blood alcohol levels on pilot performance. This research program has as its objectives the analysis of the processes involved in alcohol impairment of pilot performance at low and moderate alcohol levels, and the dissemination of such information to the scientific and aviation communities. A computer interfaced flight simulator will be used to examine pilot performance under various flight conditions and task load demands. Past work on this project has demonstrated that a low (.04%) blood alcohol concentration (BAC) can affect relatively simple flight tasks. The largest and most serious effects, however, are found when divided attention is required and the pilot most cope with multiple task demands. To investigate such situations, research will use simulator flight scenarios to investigate the effects of low BAC values on pilot performance in critical situations where 1) visual orientation is lost, 2) the aircraft is placed in unusual attitudes where the proper control inputs are essential, 3) conflicting air-traffic appears, or 4) emergencies involving various system failures occur. Other scenarios to be employed involved decision making where several courses of action are possible with differing safety implications. Interest is in the effects of alcohol on decision making processes. Increased susceptability to distraction as a function of BAC also is to be studied by examining the effects of interpolating distracting instructions or tasks while the pilot is carrying out check-list and other duties. The effects of alcohol on susceptibility to disorientation is also to be investigated. Further development of multiattribute performance models for use in evaluating alcohol's effects on simulator flight performance is also planned. A final line of investigation concerns the interaction of pilot boredom and/or fatigue with the factors discussed above. The objective of these studies is to determine if alcohol's effects, and interactions with other factors, are greater after several hours of simulator flight, a situation more comparable to many actual flying situations.